Automated assembly apparatus

ABSTRACT

To assemble nuclear fuel bundle spacers comprised of a multiplicity of rod-positioning ferrules, automated apparatus is provided comprising an indexing table mounting a plurality of identical, angularly spaced ferrule fixtures which are successively positioned at a first station for receipt of a pair of properly oriented ferrules. The table is indexed to present the ferrule pairs in turn to a second station where a spring is loaded in pre-assembly relation thereto. At the next table index position, a third station manipulates the successive fixture-mounted ferrule pairs to interlock the spring with each ferrule pair as a subasssembly which is then indexed in turn to a fourth station for assembly into a spacer fixture.

BACKGROUND OF THE INVENTION

Nuclear power reactors are a well known source of energy. In one type ofnuclear reactor the nuclear fuel is comprised of elongated rods formedof sealed cladding tubes of suitable material, such as zirconium alloy,containing uranium oxide and/or plutonium oxide as the nuclear fuel. Anumber of these fuel rods are grouped together and contained in anopen-ended tubular flow channel to form a separately removable fuelassembly or bundle. A sufficient number of these fuel bundles arearranged in a matrix, approximating a right circular cylinder, to formthe nuclear reactor core capable of self-sustained fission reaction. Thecore is submerged in a fluid, such as light water, which serves both asa coolant and as a neutron moderator.

A typical fuel bundle is formed by an array of spaced fuel rodssupported between upper and lower tie plates; the rods typically beingin excess of ten feet in length, on the order of one-half inch indiameter and spaced from one another by a fraction of an inch. Toprovide proper coolant flow past the fuel rods it is important tomaintain the rods in precisely controlled, spaced relation such as toprevent bowing and vibration during reactor operation. A plurality offuel rod spacers are thus utilized at spaced intervals along the lengthof the fuel bundle for this purpose.

Design considerations of such fuel rod bundle spacers include thefollowing: retention of rod-to-rod spacing; retention of fuel bundleshape; allowance for fuel rod thermal expansion; restriction of fuel rodvibration; ease of fuel bundle assembly; minimization of contact areasbetween spacer and fuel rods; maintenance of structural integrity of thespacer under normal and abnormal (such as seismic) loads; minimizationof reactor coolant flow distortion and restriction; maximization ofthermal limits; minimization of parasitic neutron absorption; andminimization of manufacturing costs including adaptation to automatedproduction.

Commonly assigned Matzner et al. U.S. Pat. No. 4,518,679 discloses andclaims a nuclear fuel rod bundle spacer uniquely constructed to addressthese design concerns. As disclosed therein, a spacer is formed of anarray of conjoined tubular ferrules surrounded by a peripheral supportband, each ferrule bore thus providing a passage or cell through which afuel rod or other elongated element of the fuel bundle is inserted. Theferrules are spot welded together and to the peripheral support band toprovide an assembly of high structural strength, wherein the thicknessof the metal used to form the peripheral support band and ferrules canbe minimized to reduce coolant flow resistance and parasitic neutronabsorption. Neutron absorption is further decreased by forming theferrules and peripheral support band of low neutron absorption crosssection material.

The rods or elements extending through the ferrules are centered andlaterally supported therein between rigid projections and resilientmembers. The rigid projections or stops are formed as fluted or dimpledportions of the ferrule wall at locations near the upper and lowerferrule edges to maximize the axial distance therebetween and thusenhance fuel rod support. The stops are angularly oriented to minimizeprojected area and thus disturbance of coolant flow.

The resilient members take the form of slender continuous loop springsof generally elliptical shape held captive by oppositely directed tabsformed by C-shaped cutouts in the walls of a pair of adjacent ferrules,whereby the two sides of each spring member project into the bores ofits ferrule pair. Thus, a single spring serves two ferrules in biasingthe fuel rods into contact with the two axially spaced pairs of stopspursuant to centering them in the ferrule bores.

A typical large nuclear reactor core may include on the order of 800fuel rod bundles, each with as many as seven spacers, and each spacermay comprise sixty fuel rod-positioning ferrules. From this, it is seenthat automated, expedited production of a rather involved assembly ofmany piece parts to manufacture a nuclear fuel rod spacer of suchconstruction is of vital necessity.

It is accordingly an object of the present invention to provideapparatus for assembling nuclear fuel rod bundle spacers on anexpedited, automated bundle basis.

A further object is to provide automated apparatus of theabove-character for handling, orienting and manipulating the individualfuel rod-positioning ferrules and springs pursuant to producing aferrule pair-captive spring subassembly.

An additional object is to provide automated apparatus of the abovecharacter for positioning successive ferrule pair-captive springsubassemblies in spacer assembly formation.

Another object is to provide automated assembly apparatus of theabove-character which is economical in construction, efficient inoperation, and reliable over a long service life.

Other objects of the invention will in part be obvious and in partappear hereinafter.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided automatedapparatus for assembling nuclear fuel bundle spacers, which includes afirst station for loading successive pairs of nuclear fuelrod-positioning ferrules, a second station for loading rod-positioningsprings, a third station for capturing a spring in subassembled relationwith a ferrule pair, and a forth station for assembling the resultingferrule pair-captive spring subassembly into a spacer assembly fixture;these stations being angularly spaced about a rotatably mounted indexingtable. A plurality of identical ferrule fixtures are carried by thistable for concurrent presentation of each station. The ferrule loadingstation automatically loads a pair of precisely oriented ferrules ontothe fixture thereat, and the table indexes this fixture to the springloading station where a spring is automatically placed in preassembledrelation with the ferrule pair.

When indexed to the next, spring capturing station, the ferrules of thefixture-mounted pair are automatically manipulated to capture the springin subassembled relation with the ferrule pair. The resulting ferrulepair-captive spring subassembly is indexed on its fixture by the tableto the spacer assembly station where it is picked from the ferrulefixture and placed at a predetermined location in the spacer fixture.The empty ferrule fixture is then indexed by the table back to theferrule loading station for receipt of another ferrule pair. Theassembly operation with respect to each ferrule fixture is thusperformed in four successive steps by the four stations in time phaserelation.

The invention accordingly comprises the features of construction,combination of elements, and arrangement of parts, all as set forth inthe following Detailed Description, and the scope of the invention willbe indicated in the claims.

For a full understanding of the nature and objects of the invention,reference may be had to the following Detailed Description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a elevational view, partially broken away, of a nuclear fuelbundle;

FIG. 1A is a plan view of one of the spacers utilized in the fuel bundleof FIG. 1.

FIG. 1B is a side view, partially broken away, of the nuclear fuelbundle spacer of FIG. 1A;

FIG. 2 is an elevational view of a nuclear fuel rod-positioning ferruleutilized in the spacer of FIGS. 1A and 1B;

FIG. 2A is a horizontal sectional view of a ferrule pair-springsubassembly included in the spacer of FIGS 1A and 1B;

FIG. 3 is a plan view of automated apparatus for assembling the spacerof FIGS. 1A and 1B;

FIG. 4 is a side view of the automated assembly apparatus of FIG. 3;

FIG. 5 is a plan view of one of the identical ferrule fixtures utilizedin the apparatus of FIGS. 3 and 4;

FIG. 6 is a sectional view taken along line 6--6 of FIG. 5;

FIG. 7 is a plan view of a portion of the ferrule loading stationincluded in the apparatus of FIGS. 3 and 4;

FIG. 8 is a sectional view taken along line 8--8 of FIG. 7.

FIG. 9 is an elevational view of a further portion of the ferruleloading station included in the apparatus of FIGS. 3 and 4;

FIG. 10 is a sectional view taken along 10--10 of FIG. 9;

FIG. 11 is a bottom view of the portion of the ferrule loading stationseen in FIG. 9;

FIG. 12 is an elevational view, partially in section, of the springloading station utilized in the apparatus of FIGS. 3 and 4;

FIG. 13 is a plan view of the spacer assembly station utilized in theapparatus of FIGS. 3 and 4; and

FIG. 14 is a plan view of the spacer assembly station of FIG. 13.

Corresponding reference numerals refer to like parts throughout theseveral views of the drawings.

DETAILED DESCRIPTION

The automated assembly apparatus of the present invention, generallyindicated at 20 in FIGS. 3 and 4, is disclosed in its embodiment devotedto assembling a multiplicity of fuel rod-positioning ferrules 22 into amatrix array to create a spacer, generally indicated at 24 in FIGS. 1,1A and 1B. These spacers are utilized to precisely maintain the relativepositions of a plurality of nuclear fuel rods in a fuel bundle, asdisclosed in the commonly assigned Matzner U.S. Pat. No. 4,508,679 andas generally indicated at 23 in FIG. 1 herein. Thus, each ferrule boreprovides a passage or cell through which an individual fuel rod 26 isinserted. The ferrule array is surrounded by a perimetrical band 28, towhich the ferrules in the outermost rows and columns are conjoined atcontiguous upper and lower edge points by suitable means, such as spotwelds indicated at 29. Contiguous edges of adjacent ferrules are alsoconjoined by spot welds, indicated at 31, to create a rigid spacerassembly. Suitable laser welding apparatus for this purpose is disclosedand claimed in commonly assigned Muncy et al. copending application Ser.No. 07/279010, entitled "System for Automated Welding of Parts Assemblyin Controlled Environment".

To position each fuel rod within a ferrule bore, the sidewall of eachferrule 22 is formed at each end with a pair of angularly spaced,inwardly projecting dimples or stops 30 of a precision stop height.Suitable stop forming apparatus is disclosed and claimed in commonlyassigned King et al. copending application Ser. No. 07/279009, entitled"Automated Forming Apparatus". Assembled with each different pair offerrules is a double-acting, continuous loop spring 32 which serves tobias the fuel rods against the stops of the associated ferrule pair.Thus, the fuel rods are precisely centered within each ferrule bore.Automated apparatus for checking the stop height dimensions is disclosedin commonly assigned Reeves et al. copending application Ser. No.07/279008, entitled "Automated Gauging Apparatus".

To assemble spring 32 to each ferrule pair, a C-shaped cutout 34 is cutinto the sidewall of each ferrule, as seen in FIG. 2, to provide alongitudinally elongated opening 34a and a circumferentially projectingtab 34b flanked by circumferentially extending notches 34c. In addition,circumferential slits 31 are cut into the ferrule sidewall to facilitatethe formation of stops 30, and a notch 33 is cut into one edge of theferrule to reference the relative angular positions of the slits andcutout. Automated apparatus for creating these feature cuts in theferrule sidewall is disclosed and claimed in commonly assigned Muncy etal. copending application Ser. No. 07/279007, entitled "Apparatus forMachining Intricate Feature Cuts in Thin Walled Tubular Parts".Initially, two ferrules are juxtaposted in paired side-by-side relationwith their cutout opening 34a in aligned, confronting relation. A spring32 is centered in the aligned openings, and the ferrules are thenrotated in opposite directions, as illustrated in FIG. 2A. Tabs 34b arethus swung in opposite directions to enter the open interior of spring32, which then becomes captivated in the cooperating notches 34c of theferrule pair, all as described in the above-cited Pat. No. 4,508,679.

The automated assembly apparatus 20, seen in FIGS. 3 and 4, operates tosuccessively assemble ferrules 22 into a properly oriented pair offerrules, assemble a spring 32 to each pair, and then assemble thesubassembled ferrule pair with captive spring into the matrix or "eggcrate" formation seen in FIG. 1A, all on an automated production linebasis. As seen in the plan view of FIG. 3, the automated assemblyapparatus includes a rotating table 36 which is indexed from a ferruleloading station, generally indicated at 38, a spring loading station,generally indicated at 40, a spring capturing station, generallyindicated at 42, and a spacer assembly station, generally indicated at44. This table carries four identical ferrule fixtures. generallyindicated at 46, which are angularly spaced 90° apart and thus areconcurrently presented at each station. Consequently, the assembly ofeach ferrule pair and spring subassembly into a spacer 24 isaccomplished in four steps of table 36. As each subassembly is assembledinto a spacer at station 44, successive ferrule pairs are undergoingvarious stages of assembly at stations 42, 40 and 38.

Referring jointly to FIGS. 5 and 6, each of the four ferrule pairfixtures 46 includes a fixture block 48 for mounting a pair of posts 50and 52; the later mounted on a pair of guide rods 53 for linear movementbetween a position juxtaposed post 50, as illustrated, and a positionspaced therefrom under the motivation of an air cylinder 54. As will beseen in FIG. 9, a ferrule 22 is inserted on each post while post 52 isin its spaced position relative to post 50. A pair of manipulator arms56 are rotatably mounted by fixture block 48, each having an arcuaterecess 57 partially surrounding a different one of the posts 50, 52 inclosely spaced relation. Nubs 58, protruding from the surfaces of thesearcuate recessses, are received in the indentation created in theferrule peripheral surface by the formation of lower stops 30, such thatthe arms can drivingly engage the ferrules. The arms are provided withyokes 59 which engage pins 60 carried by rods 61 slidingly mounted byfixture block 48. Thus, reciprocation of these rods 61 is seen to beeffective to rotate the ferrules on their respective posts and thuscaptivate spring 32 at station 42 and to reposition arms 56 at station38 such as to accept a pair of ferrules oriented with their C-shapedcutout openings 34a aligned in confronting relation.

Still referring to FIGS. 5 and 6, fixed post 50 is, as best seen in thelatter figure, provided with a vertically elongated cavity 62 foraccommodating an upstanding blade 64 carried on a slide 65 mounted byfixture block 48. This slide is reciprocated by an air cylinder 66 tomove the blade between its illustrated retracted position and a springcentering, closed position. Post 52 is formed with a shallow, verticallyelongated notch 67. The confronting surfaces of blade 64 and notch 67are conformed to the profile of spring 32. With the blade in itsretracted position, cavity 62 is opened to receive a spring at station40, which rests on a stop 68 projecting from post 52 into the cavity.When blade 64 is shifted to its closed position by air cylinder 66,spring 32 is centered in the confronting cutout openings 34a preparatoryto capture when the ferrules are rotated by arms 56. It is seen thatblade 64 is notched at 69 to receive spring stop 68 when blade 64 shiftsto its spring centering position. Sensors 70 strategically position infixture monitor the various operations of fixture 46.

Considering the details of ferrule loading station 38, ferrules 22 arefed successively from a suitable parts feeder, such as a vibratory bowlfeeder (not shown), through an inclined delivery tube 72 to a shuttle 74slideably mounted by a support structure 75, as seen in FIGS. 7 and 8.This shuttle is actuated by an air cylinder 76 to laterally shift eachferrule 22 exiting the delivery tube onto a pair of elongated rollers 78mounted in inclinded, closely spaced parallel relation. These rollersare driven in counter-rotation by a motor 80 to impart unindirectionalrotation to a ferrule supported thereon.

As previously noted in connection with FIG. 2, the edge of one end ofeach ferrule is keyed with a semicircular reference notch 33 whichserves as an angular reference point utilized in the forming process toprecisely locate stops 30 relative to C-shaped slot 34. Thus, rollers 78in FIGS. 7 and 8 serve to rotate a ferrule as it gravitates toward a pin84 upstanding between the rollers. As seen in FIG. 7, of the leadingedge of the ferrule contains this notch, pin 84 quickly finds andbecomes lodged therein. A sensor 86 looks for the ferrule leading edgeto detect if the notch has been found by pin 84. If it has, the pin isretracted by an air cylinder 88, and the ferrule gravitates therebeyond,as supported by the counter-rotating rollers.

On the other hand, if the pin does not find the notch, meaning that thenotch is in the ferrule trailing edge, the ferrule most be inverted. Toeffect this longitudinal reorientation, an inverter mechanism isprovided to include a U-shaped arm 90 mounted at one end to a sectorgear 92 journalled by support structure 75. This gear meshes with a rackgear 93 slideably mounted by the support structure for reciprocation byan air cylinder 94. The free end of the arm carries a thimble 95 whichis normally poised above and in alignment with the axis of a ferrulesupported in the rollers. If reorientation of a ferrule is called for bythe sensor 86, air cylinder 94 is activated to stroke rack gear such asto swing arm 90 in the downhill direction as pin 84 is retracted.Thimble 95 is thus positioned to slip into the ferrule through itsunnotched leading end as it gravitates along on rollers 78. Air cylinder94 then strokes rack gear 93 in the opposite direction to swing the armaround to the point where the ferrule is dropped back into the rollersinverted end for end. The ferrule is thus reoriented with notch 33 inits leading edge. Pin 84 remains retracted to allow the ferrule togravitate therepast on the rollers.

Stationed downstream from the retractable pin 84, as seen in FIG. 7, isa pairing shuttle 98 slidingly mounted by support structure 75 fortransverse reciprocation by an air cylinder 100. A compression spring101 biases this shuttle to quiescent position with its ferrule-receivingcavity 99 poised to accept each ferrule delivered thereto by rollers 78.Shuttle is stroked back and forth through its quiescent position by aircylinder 100 to deposit successive accepted ferrules alternately into apair of side-by-side delivery chutes 102. Ferrule detecting sensors (notshown) coordinate the operations of shuttles 74 and 98 such that, aseach ferrule is accepted by the latter, the former transfers the nextferrule in delivery tube 72 to the rollers 78.

The ferrules in chutes 102 are routed downwardly to a loading head,generally indicated at 104 in FIGS. 9, 10 and 11, where they are queuedup by an escapement mechanism, generally indicated at 106. Thismechanism includes, as seen in FIG. 10, a plate 108 which isreciprocated by an air cylinder 110 to variously position a pair offerrule stops 112 and 114 in each of a pair of side-by-side coextensivechannels 116 in communication with the lower, exit ends of chutes 120.These escappenents stops operate to release the ferrules, a pair at atime, to a orienting and loading mechanism, generally indicated at 120.

As seen in FIGS. 9 and 11, this mechanism includes a pair of opposedrollers 122 which are rotatably mounted by separate yokes 124 and drivenby separate motors 126. These yokes are slidingly mounted by guideblocks 128 for reciprocation by separate air cylinders 130. The lowerends of rollers 122 are provided with flanges 123 which serve aspositioning stops for a ferrule pair released by escapement mechanism106. Positioning springs 132 (FIG. 9), carried by yokes 124, act againsta mounting block 134 to ensure that the roller peripheries are clear ofthe ferrules as they drop down into abutment with the roller flanges123. Mounting block 134, as best seen in FIG. 11, also supports a pairof arms 136 pivotally mounted intermediate their ends at 137. Theillustrated lower ends of these arms carry locating wedges 138 which arebaised by a compression spring 139 acting in opposite directions agianstthe arms at locations below their pivot points. The ferrules, supportedon edge by the roller flangs 123, are thus urged against the rollerperipheral surfaces by locating wedges 138. An air cylinder 140 isactivated to drive its conically tipped plunger 141 between theillustrated upper ends of the arms to swing locating wedges 138 towardeach other so as not to interfere with the descent of a pair of ferrulesinto abutment with their roller flange stops. Upon arrival of theferrule pair thereat, plunger 141 is retracted, and locating wedges 138urge the ferrules into driving engagement with rollers 122. The rollermotors 126 are activated, and the ferrules are rotated on their axeswith locating wedges 138 riding on the ferrule peripheral surfaces. Theaxial positions of the rotated ferrules are maintained by bearingrollers 143. The dimensions of these locating wedges are such that theycan lodge in the longitudinal openings 34a of the ferrule C-shapedcutouts 34. As each locating wedge finds this opening the resultingincremental arm motion, induced by spring 139, is sensed by a sensor 142which issues a signal to deactivate the associated roller motor 126. Itis seen from FIG. 11 that when ferrule rotation is arrested by thelocating wedges 138, the ferrules of the pair are angularly orientedwith their cutout openings 34a in opposed, aligned relation. Aircylinder 130 are then signalled to retract the rollers 122 and clear theroller flanged from the lower flange edges. The ferrules then becomeresiliently clamped against arcuate surfaces 144 of mounting block 134by compression spring 139 acting via arms 136 and their locating wedges138 to preserve the achieved, requisitie ferrule angular orientation. Atthis point, an air cylinder 146 is activated to drive mounting block 134downwardly to seat the ferrules on posts 50 and 52 of the ferrulefixtures 46 (FIG. 5) which has been indexed to ferrule loading station38 by table 36.

Returning to FIGS. 3 and 4, a pair of stationary cams 150 and 152 arecentrally mounted one over the other, relative to table 36, while a pairof air valves 154 and 156 are mounted to the table radially inwardlyfrom each ferrule fixture 46. These valves are equipped with camfollowing actuators 155 and 157 which ride along on cams 150 and 152,respectively. From FIG. 3, it is seen that cam 150 is formed with a lobe151 which, when encountered by an actuator 155 positions its valve 154to activate the air cylinder 54 of a ferrule pair fixture 46, causingferrule post 52 to be retracted from its juxtaposed position withferrule post 50 seen in FIG. 5. This lobe is seen in FIG. 3 to extendfrom a fixture position just beyond spacer assembly station 44 in thecounterclockwise direction of table rotation (arrow 37) to a fixtureposition just beyond ferrule loading station 38. Thus, as each fixture46 leaves station 44, the ferrule post 52 is retracted from ferrule post50, such that these posts assume the requisite spaced apart relationshipseen in FIG. 9 aligned with the two ferrules held by loading block 134as it descends to insert the angularly oriented ferrules on these posts.When the table is next indexed a quarter turn, as a fixture 46 departsferrule loading station 38, its valve actuator 155 rolls off thetrailing edge of lobe 151. Fixture air cylinder 54 is then activated totranslate post 52 into juxtaposition with post 50 to bring the cutoutopenings 34a of the ferrules thereon into intimate, face-to-facerelation ready for the insertion of spring 32 upon arrival at station40.

The lobe 153 on cam 152 controls the actuation of blade positioning aircylinder 66 of each ferrule fixture 46 (FIG. 5). Again as seen in FIG.3, this lobe extends counterclockwise from a fixture position justbeyond spring loading station 40 to a fixture position just beyondspring capturing station 42. Until valve actuators 157 encounter lobe153, their valves 153 activates the air cylinders of the associatedferrule fixtures 46 such as to position blades 64 to retracted positionsseen in FIG. 6. After insertion of a spring 32 into the opened cavity 62in post 50 of a fixture 46 at station 40, lobe 153 is encountered by anvalve actuator 157 as the fixture departs the station with next tablestep. The valve 156 associated with this fixture then actuates thefixture's air cylinder 66. Blade 64 is thus shifted toward post 52 tocenter the spring 32 within the facing ferrule cutout openings 34a. Whena fixture departs spring captivation station 42, valve actuator 157rolls of the tailing end of lobe 153, and the blade 64 of this fixtureis retracted. It will be appreciated that this blade retraction does notdisturb the spring, since it has been interlocked in the closed notches34c (FIG. 2) of the ferrule pair.

Spring loading station 40, as seen in FIG. 12, includes an inclineddelivery track 160 extending from a suitable serial parts feeder, suchas a vibratory bowl feeder (not shown), for delivering a succession ofsprings 32 to a loading head 162. The springs are queued up in a channel164 formed in the loading head which is mounted by a support member 165immediately above a ferrule fixture 46 in its spring loading stationindexed position. The leading spring of this queue is stopped by ashuttle 166 in its illustrated leftmost position. This shuttle,reciprocatingly mounted by the loading head, it stroked rightward by anair cylinder 168 to pick up the leading spring in a vertical shuttlecavity 169 and is then stroked leftward to align this cavity with anopening 170 in loading head 162. An air cylinder 172 is then activatedto extend its plunger 173 and drive the spring downwardly out of shuttlecavity 169 through opening 170 into the cavity 62 left open by theretracted blade 64 of fixture post 50 (FIG. 6). The air cylinder plunger173 is retracted, and shuttle 166 picks up the next spring in the queueupon arrival of the next ferrule fixture at spring loading station 40.

As described above, the loaded spring is centered in the aligned ferruleopenings 34a by the shifting of blade 64 toward post 52 upon arrival ofa fixture 46 at spring capturing station 42. As seen in FIGS. 3 and 4,an air cylinder 176 is mounted at station 42 on a stationary platform178 underlying and extending beyond the perimeter of rotating table 36.A deck 180, mounted to this platform in elevated relation to table 36,carries a second air cylinder 182 also included at spring capturingstation 42. Referring jointly to FIGS. 3-5, the plunger 177 of aircylinder 176 and the depending extension 183 of the plunger for aircylinder 182 are positioned, upon actuation, to engage correspondingopposite ends of rods 61 (FIG. 5). The rods are thus concurrentlystroked to swing arms 56 and hence rotate the ferrules on posts 50, 52in opposite directions. The ferrules tabs 34b (FIG. 2) thus areprojected through the spring 32 in opposite directions to capture thespring in the now closed notches 34c. Preferably, station 42 alsoincludes an additional air cylinder 186 mounted by deck 180. Thevertically oriented plunger of this air cylinder carries a hold-down pad187 which is extended into lightly bearing engagement with the upperedges of the ferrules to prevent axial shifting thereof during springcapturing ferrule rotation induced by air cylinders 176 and 182.

The fixture 46 carrying the ferrule pair with captive spring is thenindexed by table 36 to spacer assembly station 44. This table step isaccompanied by retraction of spring centering blade 64, as describedabove. As seen in FIGS. 13 and 14, the spacer assembly station includesa pick and place mechanism, generally indicated at 190, operating topick the ferrule pair-spring subassembly from a fixture 46 presentedthereto and place it in a spacer fixture, generally indicated at 192.The pick and place mechanism includes a transport base 194 operating toboth vertically reciprocate along and horizontally rotate an arm 196about an axis 195. Mounted at one end of this arm is an air cylinder 198acting to vertically reciprocate gripper fingers 200 fashioned to pick aferrule pair subassembly from a fixture 46. Thus, in operation,transport base 194 lifts arm 196 and rotates it to a position wheregripper fingers 200 are vertically aligned with a fixture-borne ferrulepair subasembly presented at spacer assembly station 44. Air cylinder198 is activated to reciprocate the gripper fingers and pick thesubassembly from the fixture. Arm 196 is then rotated about axis 195 toswing the gripped subassembly around to a position above spacer fixture192. Air cylinder 198 is again activated to place the ferrule pairassembly in the spacer fixture.

It will be appreciated that, to achieve the "egg crate" spacer assemblyconfiguration seen in FIG. 1A, the placement of each ferrule pair mustbe effected at a different location in spacer fixture 192. To this end,the spacer fixture is clamped to a precision, three-axis positioningtable, generally indicated at 202. This table is programmed to linearlyposition the spacer fixture along orthogonal X and X axes, and to rotateit about a vertical Z axis. Thus, after each ferrule pair is placed inthe spacer fixture, table 202 repositions the spacer fixture so that thenext ferrule pair placement is made at an adjacent, vacant fixturelocation. As seen in FIG. 14, spacer fixture 192 is provided an array ofupstanding posts 193 located to guide the placements of successiveferrule pair subassemblies into precise positions throughout thefixture.

Returning to FIGS. 3 and 4, as a ferrule fixture 46 is indexed fromspacer assembly station 44 back to ferrule loading station 38, fixturepost 52 separation from fixture post 50 is initiated by cam 150, aspreviously described. Upon arrival at station 38, an air cylinder 210,mounted on platform 178, and an air cylinder 212, mounted by deck 180,act on fixture rods 61 (FIG. 5) to swing arms 56 back to their positionsfor accepting ferrules loaded onto the separated posts 50, 52 with thecutout openings 34a in confronting relation.

It is seen from the foregoing that the objects set forth above,including those made apparent from the preceding description, areefficiently attained, and, since certain changes may be made in thedisclosed construction without departing from the scope of theinvention, it is intended that all matters of detail contained herein betaken as illustrative and not in a limiting sense.

Having described the invention, what is claimed as new and desired tosecure by Letter Patent is:
 1. Automated apparatus for assemblingnuclear fuel bundle spacers, said apparatus comprising, incombination:A. an indexing table; B. a plurality of identical ferrulefixtures affixed to said table in angularly spaced relation, each saidferrule fixture equipped to accept a pair of ferrules; C. a ferruleloading station to which said ferrule fixtures are successively indexedby said table, said loading station operating to load a pair of ferrulesonto the one of said ferrule fixtures thereat in a predeterminedoriented relation; D. a spring loading station to which said ferrulefixtures are successively indexed from said ferrule loading station bysaid table, said spring loading station operating to load a spring ontothe one of said ferrule fixtures thereat in pre-assembled relation withthe fixture mounted pair of ferrules; E. a spring capturing station towhich said ferrule fixtures are successively indexed from said springloading station by said table, said spring capturing station operatingto manipulate the ferrule pair and spring such as to produce asubassembly consisting of a pair of ferrules and a spring interlockedtherewith in captive relation; and F. a spacer loading station to whichsaid ferrule fixtures are successively indexed from said springcapturing station by said table, said spacer loading station operatingto transfer said subassembly from the one of said ferrule fixturesthereat to a predetermined position in a spacer assembly fixture, saidferrule fixtures being successively indexed from said spacer loadingstation arount to said ferrule loading station by said table, theoperations of said stations being performed substantially concurrentlywith regard to the one of said ferrule fixtures thereat.
 2. Theautomated asembly apparatus defined in claim 1, wherein each saidferrule fixture includes a pair of upstanding posts respective mountinga pair of ferrules as loaded by said ferrule loading station.
 3. Theautomated assembly apparatus defined in claim 2, wherein each saidferrule fixture further includes a separate rotatably mountedmanipulator engageable with the ferrule mounted on each said post, saidspring capturing station including means for rotating said manipulatorsto impart incremental rotations of the ferrules on said posts pursuantto producing said subassembly.
 4. The automated assembly apparatusdefined in claim 3, wherein one post of each said ferrule fixture isprovided with a cavity adapted to receive a spring which deposited bysaid spring loading station, each said ferrule fixture further includinga positioning element operating in said cavity to shift the spring intoan assembling position relative to the fixture mounted ferrule pairprior to the incremental rotations of the ferrules by said manipulators.5. The automated assembly apparatus defined in claim 4, adapted for usewith ferrules having a sidewall containing an identical C-shaped cutouthaving a longitudinally elongated central opening and acircumferentially extending tab flanked by circumferentially extendingnotches, and for use with a spring being in the form of a double-actingloop spring, said ferrule loading station including means for angularlyorienting each pair of ferrules loaded on said ferrule fixture postswith their central openings in confronting relation and aligned withsaid cavity in said one post, said positioning element shifting thespring to said assembling position substantially centered in the centralopenings of the ferrule pair, whereby incremental rotation of theferrules by said manipulators in opposite directions swings the tabs inopposite directions into the spring open interior to interlock thespring in the notches of the ferrule pair and thereby produce saidsubassembly.
 6. The automated assembly apparatus defined in claim 5,wherein one of said posts of each said ferrule fixture is mounted formovement between spaced and juxtaposed positions with respect to theother of said posts, and means for shifting said one post to said spacedposition preparatory to the loading of a ferrule pair on said ferrulefixture by said loading station and shifting said one post to saidjuxtaposed position preparatory to the depositing of a spring into saidcavity by said spring loading station.
 7. The automated assemblyapparatus defined in claim 6, wherein each said ferrule fixture includesa first actuator for positioning said spring positioning element and asecond actuator for shifting said one post between said spaced andjuxtaposed positions, and means coordinated with the indexing of saidtable for controlling the operations of said first and second actuators.8. The automated apparatus defined in claim 7, wherein said springcapturing station includes means movable into bearing engagement withthe upper edges of the fixture mounted ferrule pair thereat to sustainthe axial positions of the ferrules on said posts during incrementalrotations thereof by said manipulators.
 9. The automated apparatusdefined in claim 7, wherein said ferrule loading station includes meansfor restoring said manipulators of the one of said ferrule fixturesthereat to respective ferrule loading positions for accepting a ferrulepair loaded on said posts with the central openings thereof inconfronting relation.
 10. The automated assembly apparatus defined inclaim 7, wherein said spacer loading station includes a positioningtable supporting said spacer fixture, and a transfer mechanism forpicking said subassemblies from said ferrule fixtures successivelypresented thereat and placing said subassemblies in said assemblyfixture at various locations determined by the positioning of saidspacer fixture by said positioning table.
 11. The automated apparatusdefined in claim 5, wherein said ferrule loading station includes firstmeans operating to ensure a predetermined longitudinal orientation ofeach ferrule, second means for arranging the ferrules in a pair ofparallel queues, and third means for successively accepting a pair offerrules, one from each said queue, and angularly orienting the ferrulesof the ferrule pair with their central opening in confronting relationpreparator to loading onto the one of said ferrule fixtures thereat. 12.The automated apparatus defined in claim 11, wherein said first means ofsaid ferrule loading station longitudinally orients each successiveferrule on the basis of a reference notch cut into one ferrule edge. 13.The automated apparatus defined in claim 12, wherein said third means ofsaid ferrule loading station includes a separate roller forindependently rotating each ferrule of a ferrule pair on its axis, and aseparate locating element bearing against the peripheral surface of eachrotating ferrule of a ferrule pair, said locating elements becominglodged in the C-shaped cutouts to arrest ferrule rotation with theferrules of a ferrule pair angularly oriented with their centralopenings in confronting relation preparatory to the loading of theferrule pair on the one of said ferrule fixtures thereat.
 14. Theautomated assembly apparatus defined in claim 13, wherein one of saidposts of each said ferrule fixture is mounted for movement betweenspaced and juxtaposed positions with respect to the other of said posts,and means for shifting said one post to said spaced position preparatoryto the loading of a ferrule pair on said ferrule fixture by said loadingstation and shifting said one post to said juxtaposed positionpreparatory to the depositing of a spring into said cavity by saidspring loading station.
 15. The automated assembly apparatus defined inclaim 14, wherein each said ferrule fixture includes a first actuatorfor positioning said spring positioning element and a second actuatorfor shifting said one post between said spaced and juxtaposed positions,and means coordinated with the indexing of said table for controllingthe operations of said first and second actuators.
 16. The automatedassembly apparatus defined in claim 15, wherein said first and secondactuator controlling means including a pair of stationary cams, aseparate pair of cam followers carried by said table in predeterminedpositional relationship with each said ferrule fixture and riding onsaid cams, and separate control elements conditioned by each of said camfollowers for controlling the operations of said first and secondactuators of each said ferrule fixture.
 17. The automated assemblyapparatus defined in claim 15, wherein said spacer loading stationincludes a positioning table supporting said spacer fixture, and atransfer mechanism for picking said subassemblies from said ferrulefixtures successively presented thereat and placing said subassembliesin said assembly fixture at various locations determined by thepositioning of said spacer fixture by said positioning table.
 18. Theautomated apparatus defined in claim 17, wherein said spring capturingstation includes means movable into bearing engagement with the upperedges of the fixture mounted ferrule pair thereat to sustain the axialpositions of the ferrules on said posts during incremental rotationsthereof by said manipulators.
 19. The automated apparatus defined inclaim 18, wherein said ferrule loading station includes means forrestoring said manipulators of the one of said ferrule fixtures thereatto respective ferrule loading positions for accepting a ferrule pairloaded on said posts with the central openings thereof in confrontingrelation.